System of communication



Feb.13,1940. la. v. L. HARTLEY 2,189,898

SYS TEM OF COMMUNICATION Original Filed Aug. 23, 1935 3 Sheets-Sheet l CIRCUIT SWEEP CIRCUIT INVENTOR R. l./! HARTLEY A T TORNE y Feh- 13, 1940- R. v. L. HARTLEY ,1 8

SYSTEM OF COMMUNICATION Original Filed Aug. 23, 1935 3 Sheets-Sheet 2 FIG. '4 B FIG. 7

' A T TORNE) Feb. 13, 1940. R. v. L. HARTLEY ,8

SYSTEM OF COMMUNICATION Original Filed Aug. 23, 1933 3 Sheets-Sheet 5 53 LPF /Nl/EN7"O/- R. KL. HARTLEY Patented Feb. 13, 1940 PATENT OFFICE SYSTEM OF COMMUNICATION- Ralph v. n Hartley, South ems. N. 1., assignor to Bell Telephone laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 23, 1933, Serial No. 886,348

Renewed May 8, 1989 29 Claims. (01. 178-737) This invention relates to systems of communication and more particularly to a method of and means for eilecting signal transmission at high efllciency and with a reduction in the eifect of interfering currents.

It has heretofore been disclosed, in connection with systems for transmitting images, to provide electrical means for reducing the distorting effect of variations in the attenuation of a line. This disclosure also includes optical means for obtaining any desired functional relation between the instantaneous value ofthe current transmitted and the brightness of the corresponding elemental area of the subject scanned for transmission.

An object of the present invention'is to provide electrical means for securing any desired functional relation between the instantaneous value of the current and light.

Another object is to provide a diil'erent type of electrical means from that disclosed inthe above mentioned proposal which may be utilized to effect the result therein set forth as well as a var'ety of other desirable results.

In one embodiment oi the invention, which may be used for transmitting pictures, image currents produced at the transmitting station are transformed into currents having instantaneous values which are logarithmically related to those of the image currents, by a cathode ray device provided with a conductive plate or anode connected to its cathode by an external path including a load circuit. The conductive plate or anode is so shaped that its vertical height varies as the logarithm oi the horizontal distance across it. The image current is used to deflect the oathode beam horizontally across the plate, while a urrent supplied by a sweeping circuit,,or a high freouency current, is used to deflect the cathode 40 beam vertically across the plate to produce in the load circuit current impulses which are util zed to control the production 01' a current having instantaneous variations logarithmically related to those of th image currents.

The invention, in its aspect considered in the preceding paragraph, may be used by providing a plate or anode of thedesired configuration, or anyequivalent structure, to produce an output cu rent having any desired non- -linear relation 0 with respect to the applied control voltage wave.

Again by using a plurality of plates or anodes properly positioned with respect to the normal or rest position of the cathode beam and providing a corresponding number of the external load circuitsconnected together diflerentially, volume compression and expansion or speech or music may be secured, or a volume indicator may be provided. By connecting the external circuits,

directly together an alternating current wave may be rectified, with or without current transformation. Moreover, the apparatus may be designed so that separate currents may be combined to eiiect detection, or to cause the amplitude or phase of one current to be modulated in accordance with variations of the other current.

Other objects and aspects of the invention will be apparent from the following description.

A detail description of the invention follows and is illustrated in the attached drawings in which,

Fig. 1 diagrammatically illustrates a picture transmitting system which includes the invention; a

Fig. 2 illustrates the plate used mitting cathode ray tube of Fig. 1';

Fig. 3 illustrates the plate included 'in the receiving cathode ray tube of Fig. 1; v

Fig. 4 illustrates curves which will be used to explain the operation of the system of Fig. 1;

Figs. 5 to 8 schematically show two plates for use in cathode ray tubes which may be used for a variety of purposes;

Fig. v9 illustrates the shape of a plate which may be used to effect modulation;

Figs. 10 and 11 illustrate schematically an arrangement which may be used when the range of signal voltag variations is wide and Fig. 12 shows a plate which may be used in the second and subsequent tubes oiFig. 11.

In picture transmission and television systems in the transsuccessive elemental areas of the picture or field of view are illuminated to cause the activation of light sensitive devices which produce an image current, the instantaneous values of which correspond to the varying tone values of successive elemental areas of the picture or field of view.

When the light sensitive device is supplied with i is focussed by a lens 2 on a picture 3 mounted on a drum 4 which is given a motion of rotation and translation, in accordance with standard practice. Scanning of successive elemental areas of the picture is thereby effected in a manner disclosed, for example, in U. S. Patent 1,706,032,

March 19, 1929, of M, B. Long, and the light passes through the picture to activate the light senmtive device, herein shown as a photoelectric cell I. to cause the production-of a picture current, the instantaneous value of which varies in accordance with the tone values of successive elemental areas of the picture.

The picture current is applied to one pair of deflecting plates 6 of a cathode ray tube I. This tube comprises a cathode 8 adapted to be heated to emit electrons by a source 8 and connected by a circuit including a battery ii to an anode ll, whereby a cathode ray beam isproduced and is projected longitudinally of the tube, a second pair of deflecting plates I 2, between which may be established an electric field at right angles to that produced between the plates 8 to which the picture current is applied, and a plate or anode it upon which the cathode beam is incident.

The plate or anode I! is of conductive material and, as shown in Fig. 2, when viewed along the longitudinal axis of the tube, its vertical height '1 varies as the logarithm of the horizontal distance .1: across it. The picture current is applied to plates 8 to cause the cathode beam to move across the plate It in the direction indicated by the double headed arrow and a current, supplied by a sweep circuit ll, causes the beam to traverse the plate It in a direction .11, i. e., at right angles to the direction indicated by the arrow 1:. A suitable sweep circuit for the purposes of the invention is disclosed in U. 8. Patent 1,618,954, January 11, 1927 of W. H. Knoop.

The plate I! may occupy any position in a plane intersecting the longitudinal axis of the tube, provided the picture current causes the beam to move along a path parallel to its a: edge and the current supplied by the sweep circuit causes the beam to move at right angles thereto and to be completely swept thereacross at a constant and relatively high rate compared with the rate of traversal produced by the picture current.

The cathode I and plate I! are connected by a load circuit externally of the tube which includes a resistance Ila adapted to be connected to the input terminals of a low-pass filter II having a cut-oil! which is below the frequency of the deflections caused by the sweeping current. The output current supplied by the filter comprises -a continuous wave, the instantaneous values of which are proportional .to the logarithm of the voltage of the picture current applied to the plates 6. The sweep-circuit may be replaced bya source supplying a current of frequency which is high compared with the highest frequency component of the picture current. If sinusoidal i in form, the amplitude of the high frequency current should be such that the cathode ray beam is only in contact with the plate it during straight portions of the successive cycles of the high frequency sweep current.

The action of the apparatus so far described may be explained by reference to Fig. 4 in which the ordinates represent current and the abscissae represent time. To simplify the exposition, the following explanation will be based on the special case in which the subject or field of view to be transmitted varies in tone value between definite limits, for example, from black to white, and in which the diiference in tone values of the elemental areas corresponds to the minimum difference in light .intensity,-used to illuminate the subject or field, that the eye is able to recognize.

Since the eye responds to illumination in accordance with Weber's law, i. e., the sensation areascs varies as the logarithm of the stimulus, the minimum difference in light intensity which the eye is able to recognize increases with the intensity of the, light.

In reproducing an individual elementary area into which the picture or scene is resolved, we are interested in the number of diflerent light intensities which can be correctly distinguished from each other. We are also interested in the range of variation of intensity, which may be measured by the ratio of the currents corresponding to the maximum and minimum light intensities which we wish to reproduce. The choice of a value of this ratio, which we shall call K, is somewhat arbitrary. If we select a size of elemental area, a value of ratio K and a number of distinguishable steps. we prescribe the degree of fidelity of reproduction. Let it be assumed that the number of distinguishable steps is the same for all areas. Call a; the amount of current (or light) corresponding to the least brightness. Since the apparent brightness varies as the logari'thm of the illumination, the currents corresponding to successive steps of equal increase of steps. .The ratio of the currents which correspond to maximum and minimum brightness is 1-(s 1)a I K a] r(s --1) In Fig. 4 curve A represents the currents produced by a photoelectric cell or other light sensitive device activated by'light controlled by elemental areas successively varying in tone values as described above. When the current indicated by curve A is applied to the pair of deflecting plates 6, and current supplied by the sweep circult, represented by curve B, is applied to the pair of deflecting plates II, the cathode ray beam will simultaneously move with respect to the plate IS in a direction along the c: axis for the duration of the signal impulse and in a direction at right angles thereto a number of times determined by the frequency of the current supplied by the sweep circuit, which should be high compared with the time period of the signal impulses. If successive signal impulses are of the same value, the beam will remain deflected in the direction a: during successive signal impulse time periods. For the sake of clarity in illustrating the operation of the apparatus, the frequency of the sweep circuit current is so chosen thatthe cathode ray beam makes four excursions during the interval required to scan each elemental area. Preferably, the frequency of the sweep current should be much higher than that indicated in Fig. 4.

Current only flows through the load circuit while the cathode ray beam is in contact with the engage the plate for correspondingly longer periods and hence the duration of the current imsively increase.

Asindicated by curve C, there will be four cur rent impulses supplied to the load circuit for the photoelectric current corresponding to each elemental area. The duration of the impulses in the period corresponding to any particular element is proportional to the logarithm of the value of the photoelectric current during that period. The four impulses will be supplied to the low-pass filter whichoperates to suppress the high frequency current components introduced by the sweep circuit and to integrate the low frequency energy of these impulses, whereby there is produced a single impulse having the same time period as the corresponding photoelectric current impulse, but having a value which is logarithmically related thereto, as indicated by curve D. With respect to curve C, it is pointed out that a given disturbing current has the same effect in causing confusion between adjacent steps of brightness, regardless of the actual degree of brightness, whereas with curve D the low brightnesses are afiected'the most. The values of the successive current variations of curve D increase arithmetically.

As described above, the cathode ray tube 1 operates, due to the modulation of the current of sweeping frequency by the picture current, to produce a modulated wave having a flat topped envelope as indicated by curve A and to transform this wave into current impulses which are of equal amplitude but vary in their time duration as. indicated by curve C.

Referring now to Fig. 1, the current variations of curve D are amplified by the device It and are transmitted over a communicating channel to a receiving station, where they are amplified by the device 11 and applied to one pair. of deflecting 4 plates l8 of a cathode ray tube l9. similar to tube l at the transmitter, but including a conductive plate 20 the height of which varies as the anti-logarithm of the distance 3:" across it. A plate of this type is shown in Fig. 3. The other pair of deflecting plates ZI is supplied from a sweep circuit 22, with current similar to that supplied by sweep circuit M at the transmitter, whereby the cathode ray beam is swept across the plate 20 to cause the production of current impulses similar to those illustrated at C n Fig. 4, but obviously of different relative durations. These impulses are applied, via the resistance lit to a low-pass filter 23, i. e.. a filter having a cutoff low compared with the frequency of the sweep circuit'current. This filter operates to suppress the high frequency components and to transform the low frequency energy into a current of the character indicated by curve A in Fig 4. This current may, if desired, be amplified by the device 24 and applied to the ribbon 25 of a light valve 25, adapted to control light of constant intensity supplied by a source 21, which is focussed by a lens 28 on a light sensitive-element 29 carried by a drum '30, which isgiven a motion of rotation and translation in synchronism and in phase with the drum 4 at the transmitter. Thus the unidirectional picture current produced at the transmitter is compressed, transmitted over a communicating channel, and expanded to its orig nal value at a receiving station to control the light applied to a light sensitive element in accordance with the tone values of the picture, whereby the latter is reproduced.

" While the operation of the system has been 1 described for a special case, its operation is not limited to such use, since a may beused in the manner described above to efl'ec't a like result when any unidirectional current having varying instantaneous values is applied to the plates 6.

The transmission circuit is herein indicated as a pair of conductors, but it should preferably include means for combining the current represented by curve D, i; e., thesig'nal current, with a wave of carrier frequency to produce modulation products which may be transmitted over one channel of a line or radiosystem. Any suitable apparatus-may be used for this purpose, such as, for example, that disclosed in II. S. Patent 1,537,535, May 12, 1925, of Kranz, which, in addition to producing modulation products per se, permits a controllable amount of unmodulated current of carrier frequency to be supplied to the channel; Use of this apparatus is desirable, because it permits the transmission of a selected amount of carrier bias for combination at the receiver with the incoming modulation products to reproduce the signal current, including its direct current component. Since the average tone value of the received picture corresponds to the value of the unmodulated carrier, its value should be controlled by the picture current. Any suitable means actuated by the picture current may be used to adjust contact l9 of the potentiometer l8, shown in the above mentioned Kranz'patent, to determinethe amplitude of the unmodulated carrier current supplied to the transmission channel.

In case the picture scanning beam is interrupted at carrier frequency, as has frequently been proposed, the apparatus shown in Fig. 5 may be used. This figure diagrammatically illustrates that the cathode ray tube 1 is provided with two plates 3| in place of the single plate I 3, to take care of both half waves of the picture modulated current applied to platesfi. Plates 3| should be of the same design as plate I 3, and they should be mounted symmetrically of the normal position of the cathode ray beam, that is, the position occupied by the beam when no picture current, which tends to deflect the cathode beam in the direction of the arrow as, is applied to the plates 6.

Sweep current being supplied to the plates l2 and picture controlled current being applied to plates 6. positively directed components-of the latter will deflect the cathode beam onto one of the plates 3| and negative components will cause it to engage the otherplate 3i, while it is being swept across the plate with which it engages by the field produced by thesweep current.

Current impulses resulting from the engagement of the cathode beam with one of the plates 3i will flow through one resistance 32 and over conductor 33 to the cathode 8, while those produced when the cathode beam engages the other plate 3| will traverse the second resistance32 and conductor 33 to cathode 8. These impulses, occurring alternately in the respective branches, including the resistances 32, will be applied to the filter l5, which passes substantially without attenuation, an alternating current of carrier ing speech or music. Current impulses, produced by the incidence of the cathode ray beam with the respective plates 3! of the tube, flow in opposite directions through the primary windings 34 of the transformer and serve to induce in the single secondary winding 35 currents that are applied to the low-pass filter l5, which, as previously described, suppresses the high frequency currents and accumulates the low frequency energy to produce a current, the instantaneous values of which are logarithmically related to those of the current applied to plates 6. The compressed current may be transmitted over a channel to a receiving station where it is applied to an apparatus of the type shown in Fig. 1 which operates to produce a-current having instantaneous values corresponding to those of the current applied to the plates 6. Alternatively the compressed current band may be supplied through a switch 36 to a meter 31, the deflection of which will be proportional to the level of the energy transmitted through the filter. This apparatus may be used as a volume indicator;

If the tube 1 is provided with a pair of plates 38, having straight edges and connected directly together as shown in Fig. 7, the apparatus may be used in the manner described above to rectify an alternating current. By properly shaping the plates, any desired degree of current transformation as well as rectification may be produced.

The invention may also be used to eflect modulation and detection. By superposing the signal current and a carrier frequency wave, or a signal modulated carrier wave and an unmodulated carrier wave, upon the deflecting plates 6 and II, respectively, of the cathode ray tube, which is provided with properly shaped conductive plates that are engaged by the cathode beam, the signal current and carrier wave may be combined to produce a signal modulated carrier wave, or the unmodulated and modulated waves may be combined to yield the signal current. Again by giving the conductive plate the desired configuration, any desired non-linear relation between the voltage applied to the plates 6 and the current in the load circuit may be obtained.

By providing the tube 1 with a pair of conductive plates 39, as shown in Fig. 8, in which the height of each plate increases as the cube of the distance from the center of the tube and differentially connecting these plates to the output circuit, as shown in Fi 6, third order modulation may be effected.

Phase modulation may be produced by providing a conductive plate 46 passing through the rest or normal position of the cathode ray beam and inclined to the direction indicated by the double headed arrow :1: as shown in Fig. 9. The signal current is applied to the deflecting plates 6, and a carrier frequency current of sinusoidal wave form or of the formsupplied by a sweep circuit is applied to the deflecting plates II. If the current applied to the deflecting plates i2 is such that the load current due to the upward sweep of the cathode ray beam is negligible, com.-

pared with that due tothe downward excursion;

i. e., if the upward sweep occurs very rapidly and the downward sweep occurs slowly, there will be a component in the load circuit of carrier frequency, the phase of which is determined by the point in the downward sweep where the beam crosses the plate 40. This will be determined by the deflection of the beam in the direction of arrow .1: and will be controlled by the signal current.

One difliculty with cathode ray tubes is that, in order to maintain the desired relations over a wide range of variation in signal voltage, the conductive plate must be prohibitively large or the diameter of the beam prohibitively small. In the case of picture and television transmission, the requirements in this respect are much more lenient than in speech and music. For example, the ratio of maximum to minimum currents that need be preserved is of the order of 10 to 1, hence it should be possible to cover the range with a practically operative tube.

In case it is desired to translate a; current having a range of variation wider than 10 to 1, this may be effected by using a plurality of tubes. Such a system will now be described in terms of the logarithmic relation described for picture transmission. Let the-tube which handles the lowest part of the intensity range be as shown in Fig. 1. If a is the minimum signal voltage, the rest position is so chosen that the cathode ray beam just reaches the plate for that voltage. For voltages up to 10a the current supplied to the load circuit increases logarithmically, and beyond that this value is made constant by providing the plate with a short section, the height of which is uniform and equal to 10a. If V1 is the signal voltage, the current i Ogr;

where b is a constant which depends on the dimensions of the plate and the constants of the system.

For

V ia the current i =o and for VfilOa, the current i =1og 10 Let'the tube which handles the next range be identical with the first except that the voltage applied to its deflecting plates Let its load current ie be added to that of the first tube. For V less-than 10a, 2': is zero and.

only the flrsttube functions. 10a. to 10011.

For values from In other words, the current added by the second tube to the constant current produced by the first tube serves to extend the desired relation over the second decade. This process may be further continued by adding more tubes, the voltage applied to the deflecting plates being reduced by a factor of ten for each successive tube.

A decade system operating in accordance with the foregoing theory and comprising three cathode ray tubes which are identical,'is shown in Fig. 10. These tubes differ from that included in the system of Fig. l, in that each includes a conductive plate Ill, which is extended at constant height beyond the upper end of its operating range, and each is provided with an electrode 4| which is energized to limit the deflection of the beam, produced by abnormal voltages, so that it does not move off the extended portion of the plate.

The purpose'of extending the plate 40 beyond tube exceeds its to the deflecting the cathode bearh when the the deflecting plates of each vide a target for voltage applied to whereby the load circuit will be supplied with current corresponding to the nominal maximum value for the respective tubes and will not'fall to zero, as would be the case if the cathode, beam were deflected past the upper margin of'the plate. Electrode 4| may comprise a fine wire parallel to the height of the-plate 40 and located at one side of the normal path of the cathodebeam between'the deflecting plates 6 and the conductive plate 40.. separate source may be applied to electrode to produce a field sufilciently strong to prevent the beam from movingbeyond the right-hand end of the extension.

Current from a sweep circuit is supplied to the deflecting plates l2 and signal current is applied plates 6 of'the tube 42 through a resistance 43, to the deflecting plates 6 of tube 44 through a connection, 45 adapted to supply a voltage corresponding to one-tenth the signal voltage, and to the deflecting plates 6 of tube 46 by means of a contact 41 engaging the resistance .43 at apoi'nthaving a voltage equal to one-hundredth 64 of the signal voltage.

In case the applied signal does not include a ratios of ill to l and 100 to direct current component, transformers having 1', respectively, may be used in place of the connections 45 and 41.

The plates 40 of the respective tubes are connected in parallel and through a potentiometer resistance to the corresponding cathodes, to -supply energy to a low-pass filter in a manner similar to and for the purpose described above in connection with Fig. 1.' o

The receiver for use with the arrangem'entof Fig. 10 includes a group of three tubes as shown in Fig. 11. These tubes are similar, but the first tube is provided with a conductive plate 48 having.

the exponential form shown in Fig. 3, and which is extended at constant height beyond the-upper end. of its operating range, for the purpose described above in connection with plates 40 of the tubes at the transmitter. Let the rest'position of the cathode beam be at the left edge of the plate, for which the current i1 is a. The other two tubes are each provided with aplate 49 similar to. that shown in Fig. 3, from the bottom of which a strip of height a has been cut off.

For the first tube, if a voltage Vi is supplied from the line to the deflecting plates resulting load current is I ill CV1 Since the received voltage is proportional to the sending current, it follows from the expression for i at the transmitter, that 1 where theconstant K can be controlled by adjustingthe gain of the .receiving apparatus If sion for i1 we find that Thus the received o 2,180,898 the operating limit 10a, 100a or 10000 is ti rpro v prescribed operating range,

;Signal current or current from a 6, the

- call for thejuse of current is made proportional to theoriginal signal voltage. If some oth'eradjustment of the receiver gain is used, the current will vary as some power of the original signal voltage other than the first.

For decade steps at the receiver, the maximum helghtof the plate should be ten times the minimum. The second tube is provided with an electrodeliil to which is applied a polarizing voltage equal to log: 10. Hence the cathode beam only reaches the left-hand edgeofthe plate 49 of mesecond tube when the voltage, supplied to the deflecting plates 6 of this tube from the line, is th'e same as that applied to the first tube to cause the current supplied ,by it to theload circuit to reach that corresponding to an original signal voltagefof 10a. This is also the value at (which the burrentin the first tubereaches its maximum andbecomes constant.

For greater values it is evident that the currentin the second .tube is given by t V I l 7 If this current is amplified ten times and added tothat of the first tube we get which is the desired relation.- This process may be extended. by increasing the polarizing'voltage by a constant amount for each additional tube and increasing the. amplification by a constant multiple. v o o To effecti't'he desired amplification the potentiometers m' the load circuits of the second and succeeding tubes are respectively connected to The amplifying factor of a polarizing voltage, that may the derived from the incoming signal orsuppliedby aseparate source, to prevent the cathode beam moving ofl the extended portions of constant height of the. plates 48 and, when voltages abnormal for the respective tubes are applied to their deflecting.

plates 8. "Battery 55 may be used to supply polarizing voltage to the electrode 54 by closing switch 56.; v

When multiple stages are used for alternating currents, a pair of conductive plates, similar to 48 and 49,may beused in the manner justdescribed. However, for stages after the first, separate tubes should be used for receiving the positive andrnegative half waves. This is made necessary by the fact that the two half waves site sign; 1. e.', the the beam from contacting with the plate at the V thatthe apparent'fbright ness varies as the logarithm of; the illumination,

polarizing voltages of opp'opolarization for preventing.

.lower end of the operating-range and forlimitthe currents corresponding to successive steps of equal increase in brightness will increase, as noted above, in geometric progression. Referring to Equation 1, the currents corresponding to the various steps are where s1 is the total number of distinguishable steps. In accordance with Equation, 2, the ratio of the currents which correspond to maximum and minimum brightness is The present invention, therefore, provides a system in which the instantaneous values of transmitted current are proportional to the logarithm ol the picture current, and hence permits the effect of interference to be distributed more evenly over the range of current employed to transmit the picture.

What is claimed:

1. A signal system comprising a cathode ray discharge device including a conductive plate of negligible resistance, a circuit connecting said plate to the cathode of said device, means controlled by signal currents and high frequency currents applied to deflecting means individual thereto for deflecting the cathode beam of said device with respect to said plate, which operates to control the production in said circuit of a current non-linearly related to the signal cur-' rent.

2. A signal system comprising means for producing signal currents, a cathode ray discharge device including electrodes energized to produce acathode ray beam, deflecting means therefor and a conductive plate of negligible resistance, a circuit connecting said plate to an electrode of said discharge device, and means for applying signal current and high frequency current to deflecting means individual thereto for efiecting deflection of said cathode beam with respect to said plate, to thereby control the production of currents having instantaneous values non-linearly related to the instantaneous values of said signal currents.

3. A wave changer comprising a cathode ray discharge device including a cathode, a conductive element of a predetermined shape and having a cathode ray beam extending between said cathode and element, a circuit connected between said cathode and said element, means for deflecting said beam in one direction and means supplied with an electric wave to cause said cathode ray beam to sweep across said element transversely to said first-mentioned deflection whereby current impulses are produced in said circuit,

and means supplied with said impulses for converting them into a wave having instantaneous values the relationship of which to the instantaneous values of the applied wave is determined by the shape of said element.

4. A wave changer comprising a cathode ray discharge device including a cathode and anode energized to produce a cathode ray beam and a conductive element having a logarithmic curvature, a circuit connecting said cathode andsaid element, means for deflecting said cathode ray beam in one direction and means supplied with a wave for effecting a second deflection of said beam, whereby current impulses controlled by said element are produced in said circuit, and

ous values bearing a logarithmic relation to the instantaneous values of the applied wave.

5. A signal system comprising'a cathode ray discharge device including a cathode and anode supplied with energy to produce a cathode ray beam, a conductive member of predetermined shape and means for deflecting said cathode beam in two directions with respect to said member, and means for supplying a signal wave to one of said deflecting means to cause the production of a wave having instantaneous values determined by the shape of .said member and nonlinearly related to those of the signal wave, means for transmitting the modified wave, and means controlled by the modified wave for reproducing the signal wave.

- non-linearly related to those of the signal wave,

means for transmitting the-modified wave; and means including a cathode ray discharge device actuated by the modified wave for controlling the production of the signal wave.

'7. An electrical system comprising a cathode ray discharge device including pairs of deflecting plates and low resistance conductive plates, a circuit connecting said conductive plates to the cathode of said device, means for supplying an electric wave to one pair of deflecting plates and current of frequency high compared to that of the electric wave to the other pair of deflecting plates to deflect the cathode beam of said device with respect to said conductive plates which opcrate to cause current flow in said circuit, and

means utilizing said current for controlling the production of electrical energy having a characteristic determined by said electric wave.

8. A system as described in claim 7 in which the conductive plates are directly connected together and are included in the circuit connection to the cathode to control the production of rectified current corresponding to the electric wave.

9. A system as described in claim 7 in which the conductive plates are differentially connected in the circuit to the cathode and current flow therein controls the production of energy having a characteristic determined by said electric wave- 10. A picture transmission or television system in which the transmitted image wave has instantaneous values corresponding to the logarithm of the light tone valued the elemental area being scanned at that instant including a cathode ray discharge device, a cathode and-a conductive plate in said device between which an electron beam extends, means to move said beam across said plate in accordance with the varying tone values of successively scanned elemental areas, means to sweep said beam across said plate at right angles to said first mentioned movement at high speed and constant distance of travel, said plate having one'edge so shaped that the perpendicular distance of any point along said edge from a line parallel to the path of said beam as traced by said first movement alone is proportional tothe logarithm of the dis-' tance traveled by said beam from its zero position when executing said first movement alone neous values of the light tone values of the elemental areas.

11. A signaling system comprising means to produce a signaling wave varying in amplitude with time, means to produce from said wave another wave consisting of a series of electric impulses of equal amplitude and time spacing but of duration corresponding to the logarithm of the amplitude of the signaling wave, and a low pass filter upon which said wave is impressed for suppressing frequencies corresponding to the time spacing of said impulses and higher frequencies.

12. A cathode ray discharge device comprising a cathode, a conductive which is non-linear, a load circuit connected between said plate and cathode, means to deflect a'beam of electrons" emitted from said cathode towardssaid plate transversely of said plate in accordance with signaling current, and meansto also deflect said beam across said plate in substantially straight lines at a frequency higher than any essential frequency of the signaling current so that the beam passes off of said plate intermittently. I

13. A signal system comprising a cathode ray discharge device including a plate of negligible resistance and selected contour, means for producing a cathode ray beam extending to said plate and deflecting means therefor, and means for supplying signal current and high frequency current to deflecting means individual thereto for effecting deflection of said cathode beam with respect to said plate for controlling the production of a current of desired amplitude relation, determined by the contour of respect to the signal current.

14. -A signal system including the use of a signal wave having a series of components extending over a frequency band, a cathode ray discharge device including a cathode and a conductive plate between which an electron beam extends, means for moving said beam across said plate in accordance with the different components of said signal wave, means to sweep said beam across said plate at right angles to said first movement and at constant speed which is high compared with the current component of maximum frequency of said signal current, said plate having one edge of a predetermined shape, and means associated with a conductive circuit connecting said cathode and said plate to control the production of a current having a definite relation, determined by the shaped the said edge of said plate, to said signal current.

15. A wave changer comprising a cathode ray discharge device including an electron emitter and a conductive plate between which an electron beam extends and means for deflecting said beam, a circuit connected between said emitter and said plate, means for simultaneously applying a signal current extending over a definite frequency range anda current of high frequency, withrespect to said signal current, to respectively different cooperating elements of said deflecting means, said deflecting means thereby causing said beam to be deflected in two direc-" tions with respect to said plate, the contour of said plate being such as to control the production in said circuit, connecting the emitter and said plate having one edge the plate, with v and and a conductive plate between which a cathode beam extends, means for moving said beam with respect to said plate in one direction by the components of said signal wave and in a second direction by high frequency current, said plate beingof selected'contour for controlling the pro,- duction of a current including components mathematically related to those of and in a frequency range determined by said signal current.

17. An apparatus for eiiecting translation of a signal wave having a series of components extending over a frequency band comprising a cathode ray discharge dev ce including a cathode a conductive plate between which a cathode beam extends, means 'i'or moving said beam with respect to said plate in one direction by the components of said signal wave and in a second direction by'high frequency current, said plate eii'ecting translation ofbetween which a cathode poner'its'of said signal wave and in a second direction by high frequency current, said plate" being of selected contour for controlling the pro- 1 duction of. a current including components loga those of and in a frequency rithmically related to range determined by the signal current.

19. A signal system comprising a cathode-ray discharge device including an electron emitter and a plate of negligible resistance and selected contour between which an and deflecting means for said beam, and means electron beam extends for applying a signal current in which successive: signals are represented by geometrically progres? sive amplitude changes with respect to said plate, to thereby control the production of a current and a high frequency} current to deflecting means-individual thereto for deflecting the cathode beam of said device' in which said successive signals are represented by arithmeticaliy pro gressive amplitude changes.- v

20. A signal system comprising acathode m discharge device includin a cathodeand a. plate of negligible resistance andselected contour between which a cathode ray beam extends a nd'jde andmeans for sup plying signal current and high frequency current fleeting means for said beam,

to deflecting means individual thereto for effects ing deflectionof said cathode be'am'jwith respect}, to said plate, the contour of which serves to con-j trol theproduction of a related to the signal current.

current logarithmically,

21. A signal device comprising strin y 8r;

cathode ray discharge and each including means, for producinganelec v e ee iv r;tr k v sponsive to difierent portionsbfasignalcurrent a H -70, H tron beam extending from an emitter to-a, target 1 i and pair of deflecting meansth erefor, and mean for connecting the vices in parallel to a control circuit.

22. In combination, a plurality of cathode ray discharge devices, respectively responsive to different; portions of a signal current and each includi means for producing an electron beam exten ng from a electron emitter to a target and pairs of deflecting means therefor, and a signal circuit connected in parallel to deflecting means of the respective devices.

23. A signal device comprising a plurality of cathode ray discharge devices respectively responsive to portions of a signal current, each portion occupying a different intensity range and each including means for producing an electron beam extending from an emitter to a target and pairs of deflecting means therefor, and means for connecting the deflecting means of said devices in parallel to a control circuit.

24. In combination, a plurality of cathode ray discharge devices respectively responsive to portions of a signal current, each portion occupying a different intensity range, and each including means for producing an electron beam extending to a target and pairs of deflecting means therefor, and a signal circuit connected in parallel to deflecting means of the respective tubes.

25. An electrical wave generator comprising an electric discharge tube'having means for producing a beam of electrons, a signal plate of electrically conducting material shaped in accordance with the desired wave shape of the electrical wave to be generated, means for deflecting said electron beam at a comparatively high frequency in a certain plane whereby said electrons strike said signal plate along, a'line, means for deflecting said electron beam periodically at a comparatively low frequency and substantially at right angles to said line, whereby the number of electrons striking said plate is varied, and means including a fllter for taking the resulting signal from said plate, said filter having a time constant which is larger than a period of said h gh frequency deflection.

26. An electrical wave generator comprising an electric discharge tube having means for producing a beam of electrons, means for deflecting said beam in a certain plane at a comparatively high frequency. means including a screen structure so positioned in the path of said beam that said deflection causes said beam to trace a line thereoni'or generating in response to deflection of said beam at right angles to said certain plane a signal voltagehaving a wave shape determined by the outline of said screen structure, means for deflecting said beam at right angles to said certain plane at a comparatively low frequency, an output circuit including a filter having a time constant which is larger than the period of one of said high frequency oscillations, and means for supplying said signal'voltage to said output circuit. i

27. An electrical wave generator comprising means for generating a beam of electrons,a target upon which said beam impinges, beam deflecting means adjacent the path of said beam, a source of high frequency waves, a source of low frequency waves, means for simultaneously applying waves from both said sources to said deflecting means, said beam deflecting means causing said waves from said high frequency source to tend to deflect said beam in one'plane only and waves from" said low frequency source to tend to deflect said beam in another plane only which is transverse to said first plane whereby said beam intersects'any plane vnear said target receiving station comprising means for generatsaid beam during a portion only of the period of g each of the waves from said high frequency source, said portions being different for different periods of the high frequency waves.

28. The combination with the elements recited in claim 27, of means for converting said train 10 of pulses into a continuous wave of varying amplitude corresponding to the varyin duration of said pulses;

29. A signal transmission system comprising at ,a transmitting station an electric wave gen- 1 erator having means for generating a beam of electrons, a target upon which said beam impinges, beam deflecting means adjacent the path of said beam, a source of high frequency waves,

a source of low frequency signal waves, means for simultaneously applying waves from both said sources to said deflecting means, said beam deflecting means causing said waves from said high frequency source to tend to deflect said beam in one planeonly and waves from said low frequency source to tend to deflect said beam in another plane only which is transverse to said first plane whereby said beam intersects any plane near said target and generally perpendicular to the paths of forming a zigzag line, means including said target for generating a pulse of electromotive force a under control of said beam during a portion only of the period of each of the waves from said high frequency source, the duration of said pulses changing with changes in the amplitude of said signal waves but at a lesser rate, means for transforming said pulses into signal voltage variations of amplitude proportional to the duration of said pulses. said signal voltage variations coro ,responding to said first-mentioned signal waves but with a compressed amplitude range, means for transmitting said signal variations to a receiving station, an electric wave generator at said ing a beam of electrons, a target upon which said beam impinges, beam deflecting means adjacent the path of said beam, a source of high frequency waves, means for simultaneously applying waves from said last-mentioned high frequency source and the signal variations received from said transmitting station to said deflecting means, said beam deflecting means causing said waves from said high frequency source to tend to deflect said beam in one plane only and waves from said low frequency source to tend to deflect said beam in another plane only which is transverse to said flrst plane whereby said beam intersects any piane near said target and generally perpendicular to the paths of said beam in a 00 series of points forming a zigzag line, and means including said target for generating a pulse of electromotive force under control of said beam during a portion only of the period of each of the waves from said high frequency source at said receiving station, the duration of said puls'es corresponding to the amplitude of said firstmentioned signal waves, and means for transforming said pulses into voltage variations of amplitude corresponding to the duration of said pulses to produce a wavelcorresponding to said original signal waves.

RALPH V. L. HARTLEY.

said beam in a series of points 30 

